The present exemplary embodiment relates to a liquid crystal (LC) device and method thereof. It finds particular application in conjunction with, for example, liquid crystal display (LCD), LC shutter, LC lens, spatial light modulator, telecommunication device, beam steering device, tunable filter, and other electrically driven LC devices, and will be described with particular reference thereto. However, it is to be appreciated that the present exemplary embodiment is also amenable to other electrooptical applications.
The reorientation of liquid crystal molecules such as nematic liquid crystal (NLC) molecules by an electric field E is used in many electrooptical applications such as Liquid Crystal displays (LCDs). Tremendous efforts have been made to improve the performance of LCDs, especially their switching time. As disclosed in D.-K. Yang and S. T. Wu, Fundamentals of Liquid Crystal Devices (John Wiley, New York, 2006), there are two phases in electric switching of a LCD. The fast “active” phase of “switch on” is driven by an applied voltage U with the characteristic time τon≈γ1d2/(∈0|Δ∈|U2), wherein ∈0 is the electric constant, d is the cell thickness, γ1 is the rotational viscosity, Δ∈=∈∥−∈⊥ is the dielectric anisotropy, and ∈∥ and ∈⊥ are the principal dielectric permittivities referred to the director {circumflex over (n)}. The characteristic time τon can be decreased by increasing U. Director reorientation in the “switch off” phase is a “passive” process driven by relaxation of elastic distortions with switch-off time τoff≈γ1d2/(π2K) that depends on the NLC properties such as γ1 and the elastic constant K, but not on the pre-applied electric field. This consideration is based on a classic picture of a NLC as a medium with no dielectric dispersion and instant dielectric response; and the dielectric torque Md=∈0Δ∈(E·{circumflex over (n)})E×{circumflex over (n)} is quadratic in E and is determined by the present values of E and {circumflex over (n)}.
Later, frequency dependence of dielectric permittivity changed this notion. According to Y. Yin, et al. Phys. Rev. Lett. 95, 087801 (2005); M. Gu, et al. Phys. Rev. E 76, 061702 (2007); and N. J. Mottram and C. V. Brown, Phys. Rev. E 74, 031703 (2006), Md depends not only on the present E and {circumflex over (n)}, but also on their past values. This “dielectric memory effect” (DME) has been studied for so-called dual frequency NLCs in which Δ∈ changes sign with the frequency f of the applied voltage.
However, there is a continuous need in the art of LC device product and process in which the “switch-off” phase can be better controlled, for example, accelerated or temporally shortened, such that the device exhibits better performance such as fast response to on/off signals. Advantageously, the present invention provides a device and method thereof that addresses this need.